The use of sorting machines to separate packages along an automated system is known. Such systems are useful in sorting a large number of packages for delivery to a number of different regions, such as zip code areas. Under the control of a computer or programmed logic controller, the packages are identified or coded as they enter the system, and may then be tracked for output at a chute or bin corresponding to the coded information.
Many deliveries are made in standardized letters of a specified size (such as 9 1/2.times.12 1/2 inches). These envelopes are often called "flats" or "flat letters" in the shipping industry. The size and construction of the flat letters is standardized so that they may be handled and sorted quickly. Because coded data is imprinted on the sides of these envelopes concerning their destination, it is preferable that the envelopes be sorted such that the information on the flats may be read by a scanner as the flat letters move along a sorting line.
U.S. Pat. No. 4,838,435 to Alexandre and U.S. Pat. No. 3,757,942 to Gunn each disclose envelope sorters which allow sorting in a generally upright position so that coded information may be read on the envelopes as they proceed along a line. The patent to Alexandre discloses a conveyor assembly for processing photograph envelopes. The assembly includes a lower, horizontal conveyor belt for moving the envelopes along the line and two guide rails which extend above and beside the lower conveyor for preventing the envelopes from falling. In this manner, the envelopes are delivered in a substantially vertical orientation. A variety of different sorting modules are provided along the conveyor for separating out packages which are too long, too thick, or unmarked. Each of these sorting modules includes an opening in one guide rail and a flap built in as part of the other guide rail. When a reject envelope approaches the sorting module, the flap is operated to reroute the envelope out through the opening in the other guide rail.
The manner of feeding the letters into the sorting system, known as the feeding mechanism, of Alexandre, dumps envelopes, standing up or lying down, on a receiving belt consisting of a horizontal endless belt. At the output of this receiving belt, the envelopes are suctioned onto a vertical, air-permeable conveyor belt by a vacuum which is located on the other side of the vertical belt. The envelopes are then fed into the horizontal conveyor belt between the two guide rails so that the envelope is maintained in the substantially vertical orientation.
Gunn discloses an envelope sorter having a lower, horizontal conveyor belt for supporting the bottom of the envelope and an upper, substantially vertical conveyor belt supporting the top of the envelope. The system relies solely on gravity for keeping the envelopes on the conveyors, and therefore the envelopes are transported down the line in an orientation which is substantially vertical, but slightly tilted from vertical. A movable sorting bin at the end of the conveyor belt moves responsive to a bar code reading on the envelopes so that the envelopes may fall from the end of the belts into a proper chute. The feeding mechanism of Gunn provides envelopes in a slanted orientation, approximately 45.degree. to vertical, down to a roller. The roller then feeds the envelopes, one at a time, onto the two conveyor belts.
Several problems exist with these prior art sorting systems. First, the feeding mechanisms for depositing the envelopes into the sorting systems are unreliable, especially for the stiffened cardboard flats that are used in the industry today. The feeding mechanism of Gunn is designed for flexible envelopes which can be easily turned and rolled onto the conveyor by the roller of that system. The roller could be inadequate for feeding stiffened cardboard flats. Moreover, the feeding mechanism of Gunn does not insure exact positioning of the envelopes on the conveyor belt, but instead drops envelopes on the conveyor belt as the roller reaches the end of the envelope. If envelopes are not positioned exactly the same in the slanted feeding trough of Gunn, the envelopes could not be fed into the conveyor system in a consistent manner. The feeding mechanism of Alexandre, on the other hand, has its own problems. The suction conveyor of that system may drop an envelope in any orientation onto the horizontal conveyor. There is also no provision in Alexandre for timed entry of the envelopes into the sorting system. Instead, the feeding mechanism just drops the envelopes randomly into the conveying system.
Another problem with the sorting systems of Alexandre and Gunn is the manner in which the sorting systems present the envelopes in a generally upright position. Because the system of Gunn relies solely on gravity to hold the envelopes in place, the vertical conveyor in that system must be tilted enough so that the envelopes will not fall forward. The tilting does not provide simple ejection from a side of the machine. The operation disclosed in Alexandre, on the other hand, delivers the envelopes in a generally upright position. However, the only supports provided in Alexandre are the two guide rails which extend above and beside the horizontal conveyor. The envelopes necessarily must lean to one of these guide rails, making the exact orientation of the envelopes unpredictable and giving an inconsistent angle for a scanner to read destination codes.
Finally, the ejection or final sorting mechanisms of Gunn and Alexandre are inefficient or would serve improperly to sort a large number of flats at a high speed. The sorting mechanism at the end of the line in Gunn requires movement of all the bins back and forth responsive to a change in sorting information. The speed of the system, therefore, is dependent upon the speed of the sorting bin moving back and forth. This system also limits the number of bins which could reasonably be used.
The ejection ports of Alexandre, on the other hand, consist of openings in the guide rails and a flap which is operated to reroute the envelopes off the line through the opening into a separate box. If an envelope is to proceed through the sorting module, no support is provided for one side of the envelope. The opening is thus a potential place for envelopes to get hung up or accidentally ejected from the line. In addition, the rerouting system of Alexandre would not work that well on a system such as is disclosed in Gunn, where the envelope is slightly slanted to the vertical.
There is a need in the art for a sorting mechanism which can more efficiently sort a large number of packages. This mechanism would preferably have a more efficient guiding and ejection system than those currently offered.